What this means for learners
Polish and Madurese share 19 sounds — roughly 51% of Madurese's inventory overlaps with Polish. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 16 sounds found only in Madurese represent the greatest pronunciation challenge for Polish speakers. The adult brain tends to map unfamiliar sounds onto the closest native equivalent — a process that produces the characteristic "accent" of a second-language speaker. Learning to hear and produce these sounds as distinct requires focused ear training, not just repetition.
Conversely, Polish has 18 sounds not used in Madurese. Native Madurese speakers learning Polish will face the mirror-image challenge with these sounds.
Phoneme inventories from PHOIBLE. Data reflects one documented inventory per language; some variation exists across dialects and sources.